EX 1 : Task#1 - Grade Calculator

int score,i;
String grade;

void setup()
{
  size(300,100);
  score = 0;
  i = 0;
}

void draw()
{
 size(300,100);
 background(0);
 fill(0);
 textSize(15);
 fill(20,255,20);
 input_score();
 print_score();
 cal_grade();
 print_grade();
 if(score>=1000){reset();}
}

void input_score()
{
  if(i==0)
  {
    if(keyPressed)
    {
      if(key == 48)  {score = score*10+0;i=1;}
      if(key == 49)  {score = score*10+1;i=1;}
      if(key == 50)  {score = score*10+2;i=1;}
      if(key == 51)  {score = score*10+3;i=1;}
      if(key == 52)  {score = score*10+4;i=1;}
      if(key == 53)  {score = score*10+5;i=1;}
      if(key == 54)  {score = score*10+6;i=1;}
      if(key == 55)  {score = score*10+7;i=1;}
      if(key == 56)  {score = score*10+8;i=1;}
      if(key == 57)  {score = score*10+9;i=1;}
    }
  }
}

void keyPressed()
{
  if(keyCode==BACKSPACE)
  {
    reset();
  }
}

void keyReleased()
{
  i=0;
}

void print_score()
{
  text("Please input your score here = "+score, 20, 40);
}

void cal_grade()
{
  if       (score >=80)                 {grade = "A" ;}
  else if  (score >= 75 && score < 80)  {grade = "B+";}
  else if  (score >= 70 && score < 75)  {grade = "B" ;}
  else if  (score >= 65 && score < 70)  {grade = "C+";}
  else if  (score >= 60 && score < 65)  {grade = "C" ;}
  else if  (score >= 55 && score < 60)  {grade = "D+";}
  else if  (score >= 50 && score < 55)  {grade = "D" ;}
  else                                  {grade = "F" ;}
}

void print_grade()
{
  if (score > 100)  {text("Error : your score is more than 100", 20, 72);}
  else              {text("Your grade is "+grade, 20, 70);}
}

void reset()
{
   score = 0;
   i = 0;
}